Field frame



Oct. 16, 1923. I 1,471,196

A. B. OWEN ET AL FIELD FRAME Filed Jan. 24, 1917 Alden .8. Owen 7770/77 as Hn/l Witness: Inventors m b W 5&2.

Attorney named at 16, 1923;

UNITED STATES.

PATENT orrics.

FIELD rmr.

' Application filed January 34,1817. lerlal Io. 144,174.

To all whom itm cmwem:

Be it known t at we, ALDEN B. Owns and THOMAS HALL, citizens of the United States, residin at Ridgway, Elk County,

Pennsylvania, ave invented certain new and useful Improvements in Field Frames,

of which the following is a s ecification.

This invention relates to improvements in the field frames of dynamo-electric mal0 chines and will be readily understood from the followin description taken in connection with t e accompanying drawing in which Fig. 1 is a face elevation of the improved field frame, a portion of this view appearing in the plane of line b of Fig.- 2: and

Fig. 2 a side elevation of the field frame, part vertical section, in the plane of line a of Fig.1.

In the drawing 1, indicates an outer field frame, to be preferably of circular form as shown, and of not unusual general construction, this outer frame being formed of cast iron and provided with the usual feet by means of which it may be bolted to a base:

2, an inner frame of wrought metal possessing magnetic permeability greater than that of the cast iron outer frame, the outer frame being shrunk upon the inner frame by the process of castin and thereby caused to grip such inner rame tightly:

3, screws passing inwardly through the cast iron frame and the wrought metal inner frame and projecting inwardly of the inner frame and adapted to screw into the heels of the pole-pieces and draw the pole-pieces firmly into mechanical and magnetic connection with the inner surface of the inner frame: a

4, the usual holes in the face of the general frame, these holes being adapted to receive screws for securing the usual bearingspiders to the faces of the frame:

5, one of the pole-pieces, having its heel secured against the inner face of the inner frame by means of one of the screws 3: and

6, a joint of abutting contact between contiguous ends of the inner frame in case the inner frame is not formed of a continuous piece of wrought metal, this joint being absent of course, if the inner frame is formed of a continuous piece of wrought metal.

In making the structure the wrought metal inner frame is placed in a mold and the cast iron outer frame is cast about it. The casting on and the shrinkage of the outerframe causes the outer. frame to grip the inner frame tightly and so brings the metal of the outer frame into intimate mechanical and m etic connection with the inner frame. he inner face of the inner frame is, if desired, later subjected to such machine operations as will facilitate the integrity of contact between the heels of the pole-pieces and the inner face of the inner frame. It is preferable that the composite frame be circular in form, as illustrated, and that side portions of the outer frame lap inwardly u on the side edges of the inner frame, the s rinkage of the casting sidewise causing these lapping portions of the cast metal outer frame to closely unite with thesides of the inner frame.

The wrought metal inner frame, being of superior magnetic conductivity, carries the greater part of the magnetism, but a part of the magnetism passes through the inner frame an into the cast iron frame, thus dividing the path of the magnetism in proportion to the relative conductive capacities of the two constituent parts of the frame.' The inner frame may, if desired, be formed of a single piece without joints but, if desired, abutting joints, as at 6, may be formed in the inner frame. For instance, the inner frame may be bent up out of a single piece of wrought metal with a gap between its contiguous ends, and if this plan of construction is followed then the gap should be of such extent that the two ends at the gap will just come together nicely as the cast iron shrinks upon the inner frame, thus avoiding such resistance to the shrinking of the cast iron as would cause the cast iron frameto burst open, and the extent of the gap should not be such as to permit the molten cast iron to flow in between the two ends of the wrought metal frame. If the inner frame is formed with one or more joints, such joints should be in such position as to be straddled by the heels of the pole-pieces.

The advantages of the above construction are not merely mechanical, that is to say, do not reside merely in features which conduce to ease of manufacture, but are fundamental, as will be seen from the following considerations CTI It is extremely desirable that the field frame of a motor or generator shall be of uniform magnetic qualities in its different sectors, i. e., spaces between poles. In particular, magnetic symmetry of these different sectors is extremely desirable. But cast iron, cast into the form of a field frame, is apt to be more or less porous and nonuniform in its structure and, therefore, in the case of a cast iron field frame, or a field frame mainly consisting of cast iron, magnetic symmetry of the sectors between the various ole ieces is apt to be lacking. But when t e field frame, and particularly a large portion thereof near the armature, is of wrought iron or steel, since wrought iron or steel are practically invariably of very uniform quality so far as different portions of any one piece are concerned, uniformity in magnetic. qualities of the different sectors of the frame is rendered practically certain.

In addition, the tight gripping of the inner frame due to the shrinking of the outer frame thereon and consequent elimination of any air gap between the inner frame and the outer frame, makes the two frames practically one in a magnetic sense; whereas even a very small air gap between the two frames would create a large magnetic resistance, such as would cause a disproportion of the lines of magnetic force to lie within the inner field frame only.

We claim l. A field frame comprising, an inner frame of wrought metal formed with a gap between contiguous ends, and an outer frame of cast iron completely surrounding and gripping tightly the inner frame and drawing and holding the two ends of the inner frame at the joint into contact with each other, combined substantially as set forth.

2. The combination with a bar of high permeabilitg bent into an annulus, of an iron generator ame in close contact with the 4. The combination with a body of material of high permeability having the form of an annulus physically interrupted at one point, of an iron generator frame in close contact with the annulus, pole pieces, and means for retaining the pole pieces in inti' mate contact with the inner surface of the annulus, the point of physical interru tion of the annulus being between one o the pole ieces and the frame.

5. he combination with a body of material of high permeability having the form of an annulus physically interrupted at one point, of an iron generator frame in close contact with the annulus and holding the ends of the annulus in physical contact at such point of physical interruption, pole pieces, and means for retaining the pole pieces in intimate contact with the inner surface of the annulus, the point of hysical interruption of the annulus being etween one of the pole pieces and the frame.

6. The method of forming field frames for dynamo electric machines, which consists in forming an annular body of material of high permeability, said annulus being physica 1y discontinuous at one point, castin asupporting iron frame about said annu us, and securing pole pieces to said annulus.

ALDEN B. OWEN. THOMAS HALL.

w. 11'. WW, L. J. A. Lnssnn. 

